Heat Holders - Mens Winter Warm Thick Bigfoot Thermal Crew Socks Size 13-15 US 91% Acrylic, 5% Nylon, 3% Poly, 1% Elastane Machine Washable 1 Pair of Mens Heat Holders - Available in size 13-15 US and in a range of great solid colours, bringing style and warmth into one ultimate sock! Heat Holders Yarn - Our specially developed thermal yarn provides high performance insulation against cold with superior moisture breathing abilities. Heat Holders Loops - Innovative knitting technology produces our unique, extra long looped cushion pile to hold in more warm air, increasing the TOG rating. Heat Holders Brushing - Finally, our expert brushing process maximises the amount of warm air held inside each sock for total warmth and all day comfort. Heat Holders TOG Rating - These socks are scientifically tested to be 7X warmer than a basic cotton sock, with a massive tog rating of 2.3!